Studies of constitutional bone marrow failure have centered on Fanconi anemia as several genes responsible for this inherited syndrome have now been identified, cloned, and sequenced. For Fanconi anemia group C, a function of the gene product has not yet been determined. Using the yeast two-hybrid system to identify interactions between FAC and other cellular proteins, GRP94 or endoplasmin, a molecular chaperone, has been shown to interact with FAC and to regulate its intracellular expression. FAC suppresses apoptosis, and when FAC is overexpressed in transgenic mice, their hematopoietic progenitors are protected from Fas-mediated death. In a unique clinical trial, the FAC gene has been introduced into human patients' blood cells and reinfused in an effort to correct the underlying bone marrow failure. The protocol has been demonstrated to be safe, and FAC has been detected in a population multipotent progenitor cells. Although blood counts have not been consistently improved, progenitor cells and mitomycin C-resistant colony numbers have increased in several treated patients after multiple cycles of gene transduction and cell reinfusion.